Disposable absorbent article with substantially continuously distributed absorbent particulate polymer material and method

ABSTRACT

A disposable absorbent core comprises first and second absorbent layers each comprising an absorbent particulate polymer material such that the absorbent particulate polymer material is substantially continuously distributed across an absorbent particulate polymer material area. A disposable absorbent article and method for making the absorbent core are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/936,102, filed on Jun. 18, 2007.

FIELD OF THE INVENTION

The present invention generally relates to an absorbent article, andmore particularly to a disposable absorbent article with absorbentparticulate polymer material, such as a diaper.

BACKGROUND OF THE INVENTION

Absorbent articles, such as disposable diapers, training pants, andadult incontinence undergarments, absorb and contain body exudates. Theyalso are intended to prevent body exudates from soiling, wetting, orotherwise contaminating clothing or other articles, such as bedding,that come in contact with the wearer. A disposable absorbent article,such as a disposable diaper, may be worn for several hours in a drystate or in a urine loaded state. Accordingly, efforts have been madetoward improving the fit and comfort of the absorbent article to thewearer, both when the article is dry and when the article is fully orpartially loaded with liquid exudate, while maintaining or enhancing theabsorbing and containing functions of the article.

Some absorbent articles, like diapers, contain an absorbent polymermaterial (also known as super absorbent polymer), such as an absorbentparticulate polymer material. Absorbent particulate polymer materialabsorbs liquid and swells and may be more effective when disposed in anabsorbent article in a certain pattern or arrangement intended foroptimal absorbency, fit, and/or comfort. Thus, it may be desirable forabsorbent particulate polymer material to remain in its intendedlocation in an absorbent article and absorbent particulate polymermaterial, therefore, is desirably immobilized in the absorbent articlesuch that the absorbent particulate polymer material remains immobilizedwhen the absorbent article is dry and when it is wet.

In addition to being absorbent, absorbent articles, such as diapers, maydesirably be thin and flexible, for ease and comfort in use and for moreconvenient and neat packaging and storage. Absorbent articles, which mayoften be used in large quantities, may also desirably be inexpensive.Some technologies of immobilizing absorbent particulate polymer materialin an absorbent article add bulk to the absorbent article and therebyincrease thickness, reduce flexibility, and/or increase cost of theabsorbent article. Other technologies for immobilizing absorbentparticulate polymer material in an absorbent article may not be aseffective in maintaining immobilization when the absorbent article is inthe wet state as when in the dry state. Accordingly, there remains aneed for a thin, flexible, and/or inexpensive absorbent articlecontaining absorbent particulate polymer material with enhancedimmobilization of the absorbent particulate polymer material in thearticle in dry and wet states.

SUMMARY OF THE INVENTION

The present invention addresses one or more technical problems describedabove and provides a disposable absorbent article which may comprise achassis and an absorbent core. The chassis may contain a topsheet and abacksheet. The absorbent core may be located between the topsheet andthe backsheet and may include first and second absorbent layers. Thefirst absorbent layer may include first substrate and the secondabsorbent layer may include a second substrate. The first and secondabsorbent layers may further include absorbent particulate polymermaterial deposited on the first and second substrates and thermoplasticadhesive material covering the absorbent particulate polymer material onthe respective first and second substrates.

The first and second absorbent layers may be combined together such thatat least a portion of said thermoplastic adhesive material of said firstabsorbent layer contacts at least a portion of the thermoplasticadhesive material of said second absorbent layer, the absorbentparticulate polymer material is disposed between the first and secondsubstrates in an absorbent particulate polymer area, and the absorbentparticulate polymer material is substantially continuously distributedacross the absorbent particulate polymer material area.

According to another aspect of this invention, an absorbent core asdescribed herein above is provided.

According to yet another aspect of this invention, a method of making adisposable absorbent article is provided comprising depositing absorbentparticulate polymer material on a first substrate in a first pattern toform a first absorbent layer such that the absorbent particulate polymermaterial is discontinuously distributed on the first substrate,depositing absorbent particulate polymer material on a second substratein a second pattern to form a second absorbent layer such that theabsorbent particulate polymer material is discontinuously distributed onthe second substrate, depositing a thermoplastic layer on the absorbentparticulate polymer material and the first and second substrates tocover the absorbent particulate polymer material on the first and secondsubstrates, and combining the first and second absorbent layers togethersuch that at least a portion of said thermoplastic adhesive material ofsaid first absorbent layer contacts at least a portion of thethermoplastic adhesive material of said second absorbent layer, theabsorbent particulate polymer material is disposed between the first andsecond substrates in an absorbent particulate polymer material area, andthe absorbent particulate polymer material is substantially continuouslydistributed across the absorbent polymer material area.

Other features and advantages of the invention may be apparent fromreading the following detailed description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a diaper in accordance with an embodiment ofthe present invention.

FIG. 2 is a cross sectional view of the diaper shown in FIG. 1 takenalong the sectional line 2-2 of FIG. 1.

FIG. 3 is a partial cross sectional view of an absorbent core layer inaccordance with an embodiment of this invention.

FIG. 4 is a partial cross sectional view of an absorbent core layer inaccordance with another embodiment of this invention.

FIG. 5 is a plan view of the absorbent core layer illustrated in FIG. 3.

FIG. 6 is a plan view of a second absorbent core layer in accordancewith an embodiment of this invention.

FIG. 7 a is a partial sectional view of an absorbent core comprising acombination of the first and second absorbent core layers illustrated inFIGS. 5 and 6.

FIG. 7 b is a partial sectional view of an absorbent core comprising acombination of the first and second absorbent core layers illustrated inFIGS. 5 and 6.

FIG. 8 is a plan view of the absorbent core illustrated in FIGS. 7 a and7 b.

FIG. 9 is a schematic representation of a rheometer.

FIG. 10 is a schematic illustration of a process for making an absorbentcore in accordance with an embodiment of this invention.

FIG. 11 is a partial sectional view of an apparatus for making anabsorbent core in accordance with an embodiment of this invention.

FIG. 12 is a perspective view of the printing roll illustrated in FIG.11.

FIG. 13 is a partial sectional view of the printing roll illustrated inFIG. 12 showing an absorbent particulate polymer material reservoir.

FIG. 14 is a perspective view of the supporting roll illustrated in FIG.12.

DETAILED DESCRIPTION OF THE INVENTION

“Absorbent article” refers to devices that absorb and contain bodyexudates, and, more specifically, refers to devices that are placedagainst or in proximity to the body of the wearer to absorb and containthe various exudates discharged from the body. Absorbent articles mayinclude diapers, training pants, adult incontinence undergarments,feminine hygiene products, breast pads, care mats, bibs, wound dressingproducts, and the like. As used herein, the term “body fluids” or “bodyexudates” includes, but is not limited to, urine, blood, vaginaldischarges, breast milk, sweat and fecal matter.

“Absorbent core” means a structure typically disposed between a topsheetand backsheet of an absorbent article for absorbing and containingliquid received by the absorbent article and may comprise one or moresubstrates, absorbent polymer material disposed on the one or moresubstrates, and a thermoplastic composition on the absorbent particulatepolymer material and at least a portion of the one or more substratesfor immobilizing the absorbent particulate polymer material on the oneor more substrates. In a multilayer absorbent core, the absorbent coremay also include a cover layer. The one or more substrates and the coverlayer may comprise a nonwoven. Further, the absorbent core issubstantially cellulose free. The absorbent core does not include anacquisition system, a topsheet, or a backsheet of the absorbent article.In a certain embodiment, the absorbent core would consist essentially ofthe one or more substrates, the absorbent polymer material, thethermoplastic composition, and optionally the cover layer.

“Absorbent polymer material,” “absorbent gelling material,” “AGM,”“superabsorbent,” and “superabsorbent material” are used hereininterchangeably and refer to cross linked polymeric materials that canabsorb at least 5 times their weight of an aqueous 0.9% saline solutionas measured using the Centrifuge Retention Capacity test (Edana441.2-01).

“Absorbent particulate polymer material” is used herein to refer to anabsorbent polymer material which is in particulate form so as to beflowable in the dry state.

“Absorbent particulate polymer material area” as used herein refers tothe area of the core wherein the first substrate 64 and second substrate72 are separated by a multiplicity of superabsorbent particles. In FIG.8, the boundary of the absorbent particulate polymer material area isdefined by the perimeter of the overlapping circles. There may be someextraneous superabsorbent particles outside of this perimeter betweenthe first substrate 64 and second substrate 72.

“Airfelt” is used herein to refer to comminuted wood pulp, which is aform of cellulosic fiber.

“Comprise,” “comprising,” and “comprises” are open ended terms, eachspecifies the presence of what follows, e.g., a component, but does notpreclude the presence of other features, e.g., elements, steps,components known in the art, or disclosed herein.

“Consisting essentially of” is used herein to limit the scope of subjectmatter, such as that in a claim, to the specified materials or steps andthose that do not materially affect the basic and novel characteristicsof the subject matter.

“Disposable” is used in its ordinary sense to mean an article that isdisposed or discarded after a limited number of usage events overvarying lengths of time, for example, less than about 20 events, lessthan about 10 events, less than about 5 events, or less than about 2events.

“Diaper” refers to an absorbent article generally worn by infants andincontinent persons about the lower torso so as to encircle the waistand legs of the wearer and that is specifically adapted to receive andcontain urinary and fecal waste. As used herein, term “diaper” alsoincludes “pants” which is defined below.

“Fiber” and “filament” are used interchangeably.

A “nonwoven” is a manufactured sheet, web or batt of directionally orrandomly orientated fibers, bonded by friction, and/or cohesion and/oradhesion, excluding paper and products which are woven, knitted, tufted,stitch-bonded incorporating binding yarns or filaments, or felted bywet-milling, whether or not additionally needled. The fibers may be ofnatural or man-made origin and may be staple or continuous filaments orbe formed in situ. Commercially available fibers have diameters rangingfrom less than about 0.001 mm to more than about 0.2 mm and they come inseveral different forms: short fibers (known as staple, or chopped),continuous single fibers (filaments or monofilaments), untwisted bundlesof continuous filaments (tow), and twisted bundles of continuousfilaments (yarn). Nonwoven fabrics can be formed by many processes suchas meltblowing, spunbonding, solvent spinning, electrospinning, andcarding. The basis weight of nonwoven fabrics is usually expressed ingrams per square meter (gsm).

“Pant” or “training pant”, as used herein, refer to disposable garmentshaving a waist opening and leg openings designed for infant or adultwearers. A pant may be placed in position on the wearer by inserting thewearer's legs into the leg openings and sliding the pant into positionabout a wearer's lower torso. A pant may be preformed by any suitabletechnique including, but not limited to, joining together portions ofthe article using refastenable and/or non-refastenable bonds (e.g.,seam, weld, adhesive, cohesive bond, fastener, etc.). A pant may bepreformed anywhere along the circumference of the article (e.g., sidefastened, front waist fastened). While the terms “pant” or “pants” areused herein, pants are also commonly referred to as “closed diapers,”“prefastened diapers,” “pull-on diapers,” “training pants,” and“diaper-pants”. Suitable pants are disclosed in U.S. Pat. No. 5,246,433,issued to Hasse, et al. on Sep. 21, 1993; U.S. Pat. No. 5,569,234,issued to Buell et al. on Oct. 29, 1996; U.S. Pat. No. 6,120,487, issuedto Ashton on Sep. 19, 2000; U.S. Pat. No. 6,120,489, issued to Johnsonet al. on Sep. 19, 2000; U.S. Pat. No. 4,940,464, issued to Van Gompelet al. on Jul. 10, 1990; U.S. Pat. No. 5,092,861, issued to Nomura etal. on Mar. 3, 1992; U.S. Patent Publication No. 2003/0233082 A1,entitled “Highly Flexible And Low Deformation Fastening Device”, filedon Jun. 13, 2002; U.S. Pat. No. 5,897,545, issued to Kline et al. onApr. 27, 1999; U.S. Pat. No. 5,957,908, issued to Kline et al on Sep.28, 1999.

“Substantially cellulose free” is used herein to describe an article,such as an absorbent core, that contains less than 10% by weightcellulosic fibers, less than 5% cellulosic fibers, less than 1%cellulosic fibers, no cellulosic fibers, or no more than an immaterialamount of cellulosic fibers. An immaterial amount of cellulosic materialwould not materially affect the thinness, flexibility, or absorbency ofan absorbent core.

“Substantially continuously distributed” as used herein indicates thatwithin the absorbent particulate polymer material area, the firstsubstrate 64 and second substrate 72 are separated by a multiplicity ofsuperabsorbent particles. It is recognized that there may be minorincidental contact areas between the first substrate 64 and secondsubstrate 72 within the absorbent particulate polymer material area.Incidental contact areas between the first substrate 64 and secondsubstrate 72 may be intentional or unintentional (e.g. manufacturingartifacts) but do not form geometries such as pillows, pockets, tubes,quilted patterns and the like.

“Thermoplastic adhesive material” as used herein is understood tocomprise a polymer composition from which fibers are formed and appliedto the superabsorbent material with the intent to immobilize thesuperabsorbent material in both the dry and wet state. The thermoplasticadhesive material of the present invention forms a fibrous network overthe superabsorbent material.

“Thickness” and “caliper” are used herein interchangeably.

FIG. 1 is a plan view of a diaper 10 according to a certain embodimentof the present invention. The diaper 10 is shown in its flat out,uncontracted state (i.e., without elastic induced contraction) andportions of the diaper 10 are cut away to more clearly show theunderlying structure of the diaper 10. A portion of the diaper 10 thatcontacts a wearer is facing the viewer in FIG. 1. The diaper 10generally may comprise a chassis 12 and an absorbent core 14 disposed inthe chassis.

The chassis 12 of the diaper 10 in FIG. 1 may comprise the main body ofthe diaper 10. The chassis 12 may comprise an outer covering 16including a topsheet 18, which may be liquid pervious, and/or abacksheet 20, which may be liquid impervious. The absorbent core 14 maybe encased between the topsheet 18 and the backsheet 20. The chassis 12may also include side panels 22, elasticized leg cuffs 24, and anelastic waist feature 26.

The leg cuffs 24 and the elastic waist feature 26 may each typicallycomprise elastic members 28. One end portion of the diaper 10 may beconfigured as a first waist region 30 of the diaper 10. An opposite endportion of the diaper 10 may be configured as a second waist region 32of the diaper 10. An intermediate portion of the diaper 10 may beconfigured as a crotch region 34, which extends longitudinally betweenthe first and second waist regions 30 and 32. The waist regions 30 and32 may include elastic elements such that they gather about the waist ofthe wearer to provide improved fit and containment (elastic waistfeature 26). The crotch region 34 is that portion of the diaper 10which, when the diaper 10 is worn, is generally positioned between thewearer's legs.

The diaper 10 is depicted in FIG. 1 with its longitudinal axis 36 andits transverse axis 38. The periphery 40 of the diaper 10 is defined bythe outer edges of the diaper 10 in which the longitudinal edges 42 rungenerally parallel to the longitudinal axis 36 of the diaper 10 and theend edges 44 run between the longitudinal edges 42 generally parallel tothe transverse axis 38 of the diaper 10. The chassis 12 may alsocomprise a fastening system, which may include at least one fasteningmember 46 and at least one stored landing zone 48.

The diaper 20 may also include such other features as are known in theart including front and rear ear panels, waist cap features, elasticsand the like to provide better fit, containment and aestheticcharacteristics. Such additional features are well known in the art andare e.g., described in U.S. Pat. Nos. 3,860,003 and 5,151,092.

In order to keep the diaper 10 in place about the wearer, at least aportion of the first waist region 30 may be attached by the fasteningmember 46 to at least a portion of the second waist region 32 to formleg opening(s) and an article waist. When fastened, the fastening systemcarries a tensile load around the article waist. The fastening systemmay allow an article user to hold one element of the fastening system,such as the fastening member 46, and connect the first waist region 30to the second waist region 32 in at least two places. This may beachieved through manipulation of bond strengths between the fasteningdevice elements.

According to certain embodiments, the diaper 10 may be provided with are-closable fastening system or may alternatively be provided in theform of a pant-type diaper. When the absorbent article is a diaper, itmay comprise a re-closable fastening system joined to the chassis forsecuring the diaper to a wearer. When the absorbent article is apant-type diaper, the article may comprise at least two side panelsjoined to the chassis and to each other to form a pant. The fasteningsystem and any component thereof may include any material suitable forsuch a use, including but not limited to plastics, films, foams,nonwoven, woven, paper, laminates, fiber reinforced plastics and thelike, or combinations thereof. In certain embodiments, the materialsmaking up the fastening device may be flexible. The flexibility mayallow the fastening system to conform to the shape of the body and thus,reduce the likelihood that the fastening system will irritate or injurethe wearer's skin.

For unitary absorbent articles, the chassis 12 and absorbent core 14 mayform the main structure of the diaper 10 with other features added toform the composite diaper structure. While the topsheet 18, thebacksheet 20, and the absorbent core 14 may be assembled in a variety ofwell-known configurations, preferred diaper configurations are describedgenerally in U.S. Pat. No. 5,554,145 entitled “Absorbent Article WithMultiple Zone Structural Elastic-Like Film Web Extensible Waist Feature”issued to Roe et al. on Sep. 10, 1996; U.S. Pat. No. 5,569,234 entitled“Disposable Pull-On Pant” issued to Buell et al. on Oct. 29, 1996; andU.S. Pat. No. 6,004,306 entitled “Absorbent Article WithMulti-Directional Extensible Side Panels” issued to Robles et al. onDec. 21, 1999.

The topsheet 18 in FIG. 1 may be fully or partially elasticized or maybe foreshortened to provide a void space between the topsheet 18 and theabsorbent core 14. Exemplary structures including elasticized orforeshortened topsheets are described in more detail in U.S. Pat. No.5,037,416 entitled “Disposable Absorbent Article Having ElasticallyExtensible Topsheet” issued to Allen et al. on Aug. 6, 1991; and U.S.Pat. No. 5,269,775 entitled “Trisection Topsheets for DisposableAbsorbent Articles and Disposable Absorbent Articles Having SuchTrisection Topsheets” issued to Freeland et al. on Dec. 14, 1993.

The backsheet 26 may be joined with the topsheet 18. The backsheet 20may prevent the exudates absorbed by the absorbent core 14 and containedwithin the diaper 10 from soiling other external articles that maycontact the diaper 10, such as bed sheets and undergarments. In certainembodiments, the backsheet 26 may be substantially impervious to liquids(e.g., urine) and comprise a laminate of a nonwoven and a thin plasticfilm such as a thermoplastic film having a thickness of about 0.012 mm(0.5 mil) to about 0.051 mm (2.0 mils). Suitable backsheet films includethose manufactured by Tredegar Industries Inc. of Terre Haute, Ind. andsold under the trade names X15306, X10962, and X10964. Other suitablebacksheet materials may include breathable materials that permit vaporsto escape from the diaper 10 while still preventing liquid exudates frompassing through the backsheet 10. Exemplary breathable materials mayinclude materials such as woven webs, nonwoven webs, composite materialssuch as film-coated nonwoven webs, and microporous films such asmanufactured by Mitsui Toatsu Co., of Japan under the designation ESPOIRNO and by EXXON Chemical Co., of Bay City, Tex., under the designationEXXAIRE. Suitable breathable composite materials comprising polymerblends are available from Clopay Corporation, Cincinnati, Ohio under thename HYTREL blend P18-3097. Such breathable composite materials aredescribed in greater detail in PCT Application No. WO 95/16746,published on Jun. 22, 1995 in the name of E.I. DuPont. Other breathablebacksheets including nonwoven webs and apertured formed films aredescribed in U.S. Pat. No. 5,571,096 issued to Dobrin et al. on Nov. 5,1996.

In certain embodiments, the backsheet of the present invention may havea water vapor transmission rate (WVTR) of greater than about 2000 g/24h/m², greater than about 3000 g/24 h/m², greater than about 5000 g/24h/m², greater than about 6000 g/24 h/m², greater than about 7000 g24h/m², greater than about 8000 g/24 h/m², greater than about 9000 g/24h/m², greater than about 10000 g/24 h/m², greater than about 11000 g/24h/m², greater than about 12000 g/24 h/m², greater than about 15000 g/24h/m², measured according to WSP 70.5 (08) at 37.8° C. and 60% RelativeHumidity.

FIG. 2 shows a cross section of FIG. 1 taken along the sectional line2-2 of FIG. 1. Starting from the wearer facing side, the diaper 10 maycomprise the topsheet 18, the components of the absorbent core 14, andthe backsheet 20. According to a certain embodiment, diaper 10 may alsocomprise an acquisition system 50 disposed between the liquid permeabletopsheet 18 and a wearer facing side of the absorbent core 14. Theacquisition system 50 may be in direct contact with the absorbent core.The acquisition system 50 may comprise a single layer or multiplelayers, such as an upper acquisition layer 52 facing towards thewearer's skin and a lower acquisition 54 layer facing the garment of thewearer. According to a certain embodiment, the acquisition system 50 mayfunction to receive a surge of liquid, such as a gush of urine. In otherwords, the acquisition system 50 may serve as a temporary reservoir forliquid until the absorbent core 14 can absorb the liquid.

In a certain embodiment, the acquisition system 50 may comprisechemically cross-linked cellulosic fibers. Such cross-linked cellulosicfibers may have desirable absorbency properties. Exemplary chemicallycross-linked cellulosic fibers are disclosed in U.S. Pat. No. 5,137,537.In certain embodiments, the chemically cross-linked cellulosic fibersare cross-linked with between about 0.5 mole % and about 10.0 mole % ofa C₂ to C₉ polycarboxylic cross-linking agent or between about 1.5 mole% and about 6.0 mole % of a C₂ to C₉ polycarboxylic cross-linking agentbased on glucose unit. Citric acid is an exemplary cross-linking agent.In other embodiments, polyacrylic acids may be used. Further, accordingto certain embodiments, the cross-linked cellulosic fibers have a waterretention value of about 25 to about 60, or about 28 to about 50, orabout 30 to about 45. A method for determining water retention value isdisclosed in U.S. Pat. No. 5,137,537. According to certain embodiments,the cross-linked cellulosic fibers may be crimped, twisted, or curled,or a combination thereof including crimped, twisted, and curled.

In a certain embodiment, one or both of the upper and lower acquisitionlayers 52 and 54 may comprise a non-woven, which may be hydrophilic.Further, according to a certain embodiment, one or both of the upper andlower acquisition layers 52 and 54 may comprise the chemicallycross-linked cellulosic fibers, which may or may not form part of anonwoven material. According to an exemplary embodiment, the upperacquisition layer 52 may comprise a nonwoven, without the cross-linkedcellulosic fibers, and the lower acquisition layer 54 may comprise thechemically cross-linked cellulosic fibers. Further, according to anembodiment, the lower acquisition layer 54 may comprise the chemicallycross-linked cellulosic fibers mixed with other fibers such as naturalor synthetic polymeric fibers. According to exemplary embodiments, suchother natural or synthetic polymeric fibers may include high surfacearea fibers, thermoplastic binding fibers, polyethylene fibers,polypropylene fibers, PET fibers, rayon fibers, lyocell fibers, andmixtures thereof. According to a particular embodiment, the loweracquisition layer 54 has a total dry weight, the cross-linked cellulosicfibers are present on a dry weight basis in the upper acquisition layerin an amount from about 30% to about 95% by weight of the loweracquisition layer 54, and the other natural or synthetic polymericfibers are present on a dry weight basis in the lower acquisition layer54 in an amount from about 70% to about 5% by weight of the loweracquisition layer 54. According to another embodiment, the cross-linkedcellulosic fibers are present on a dry weight basis in the firstacquisition layer in an amount from about 80% to about 90% by weight ofthe lower acquisition layer 54, and the other natural or syntheticpolymeric fibers are present on a dry weight basis in the loweracquisition layer 54 in an amount from about 20% to about 10% by weightof the lower acquisition layer 54.

According to a certain embodiment, the lower acquisition layer 54desirably has a high fluid uptake capability. Fluid uptake is measuredin grams of absorbed fluid per gram of absorbent material and isexpressed by the value of “maximum uptake.” A high fluid uptakecorresponds therefore to a high capacity of the material and isbeneficial, because it ensures the complete acquisition of fluids to beabsorbed by an acquisition material. According to exemplary embodiments,the lower acquisition layer 54 has a maximum uptake of about 10 g/g.

A relevant attribute of the upper acquisition layer 54 is its MedianDesorption Pressure, MDP. The MDP is a measure of the capillary pressurethat is required to dewater the lower acquisition layer 54 to about 50%of its capacity at 0 cm capillary suction height under an appliedmechanical pressure of 0.3 psi. Generally, a relatively lower MDP may beuseful. The lower MDP may allow the lower acquisition layer 54 to moreefficiently drain the upper acquisition material. Without wishing to bebound by theory, a given distribution material may have a definablecapillary suction. The ability of the lower acquisition layer 54 to moveliquid vertically via capillary forces will be directly impacted bygravity and the opposing capillary forces associated with desorption ofthe upper acquisition layer. Minimizing these capillary forces maypositively impact the performance of the lower acquisition layer 54.However, in a certain embodiment the lower acquisition layer 54 may alsohave adequate capillary absorption suction in order to drain the layersabove (upper acquisition layer 52 and topsheet 18, in particular) and totemporarily hold liquid until the liquid can be partitioned away by theabsorbent core components. Therefore, in a certain embodiment, the loweracquisition layer 54 may have a minimum MDP of greater than 5 cm.Further, according to exemplary embodiments, the lower acquisition layer54 has an MDP value of less than about 20.5 cm H₂O, or less than about19 cm H₂O, or less than about 18 cm H₂O to provide for fast acquisition.

The methods for determining MDP and maximum uptake are disclosed in U.S.patent application Ser. No. 11/600,691 (Flohr et al.). For example,according to a first embodiment, the lower acquisition layer 54 maycomprise about 70% by weight of chemically cross-linked cellulosefibers, about 10% by weight polyester (PET), and about 20% by weightuntreated pulp fibers. According to a second embodiment, the loweracquisition layer 54 may comprise about 70% by weight chemicallycross-linked cellulose fibers, about 20% by weight lyocell fibers, andabout 10% by weight PET fibers. According to a third embodiment, thelower acquisition layer 54 may comprise about 68% by weight chemicallycross-linked cellulose fibers, about 16% by weight untreated pulpfibers, and about 16% by weight PET fibers. In one embodiment, the loweracquisition layer 54 may comprise from about 90-100% by weightchemically cross-linked cellulose fibers.

Suitable non-woven materials for the upper and lower acquisition layers52 and 54 include, but are not limited to SMS material, comprising aspunbonded, a melt-blown and a further spunbonded layer. In certainembodiments, permanently hydrophilic non-wovens, and in particular,nonwovens with durably hydrophilic coatings are desirable. Anothersuitable embodiment comprises a SMMS-structure. In certain embodiments,the non-wovens are porous.

In certain embodiments, suitable non-woven materials may include, butare not limited to synthetic fibers, such as PE, PET, and PP. Aspolymers used for nonwoven production may be inherently hydrophobic,they may be coated with hydrophilic coatings. One way to producenonwovens with durably hydrophilic coatings, is via applying ahydrophilic monomer and a radical polymerization initiator onto thenonwoven, and conducting a polymerization activated via UV lightresulting in monomer chemically bound to the surface of the nonwoven asdescribed in co-pending U.S. Patent Publication No. 2005/0159720.Another way to produce nonwovens with durably hydrophilic coatings is tocoat the nonwoven with hydrophilic nanoparticles as described inco-pending applications U.S. Pat. No. 7,112,621 to Rohrbaugh et al. andin PCT Application Publication WO 02/064877.

Typically, nanoparticles have a largest dimension of below 750 nm.Nanoparticles with sizes ranging from 2 to 750 nm may be economicallyproduced. An advantage of nanoparticles is that many of them can beeasily dispersed in water solution to enable coating application ontothe nonwoven, they typically form transparent coatings, and the coatingsapplied from water solutions are typically sufficiently durable toexposure to water. Nanoparticles can be organic or inorganic, syntheticor natural. Inorganic nanoparticles generally exist as oxides,silicates, and/or, carbonates. Typical examples of suitablenanoparticles are layered clay minerals (e.g., LAPONITE™ from SouthernClay Products, Inc. (USA), and Boehmite alumina (e.g., Disperal P2™ fromNorth American Sasol. Inc.). According to a certain embodiment, asuitable nanoparticle coated non-woven is that disclosed in theco-pending patent application Ser. No. 10/758,066 entitled “Disposableabsorbent article comprising a durable hydrophilic core wrap” toEkaterina Anatolyevna Ponomarenko and Mattias NMN Schmidt.

Further useful non-wovens are described in U.S. Pat. No. 6,645,569 toCramer et al., U.S. Pat. No. 6,863,933 to Cramer et al., U.S. Pat. No.7,112,621 to Rohrbaugh et al., and co-pending patent application Ser.No. 10/338,603 to Cramer et al. and Ser. No. 10/338,610 to Cramer et al.

In some cases, the nonwoven surface can be pre-treated with high energytreatment (corona, plasma) prior to application of nanoparticlecoatings. High energy pre-treatment typically temporarily increases thesurface energy of a low surface energy surface (such as PP) and thusenables better wetting of a nonwoven by the nanoparticle dispersion inwater.

Notably, permanently hydrophilic non-wovens are also useful in otherparts of an absorbent article. For example, topsheets and absorbent corelayers comprising permanently hydrophilic non-wovens as described abovehave been found to work well.

According to a certain embodiment, the upper acquisition layer 52 maycomprise a material that provides good recovery when external pressureis applied and removed. Further, according to a certain embodiment, theupper acquisition layer 52 may comprise a blend of different fibersselected, for example from the types of polymeric fibers describedabove. In some embodiments, at least a portion of the fibers may exhibita spiral-crimp which has a helical shape. In some embodiments, the upperacquisition layer 52 may comprise fibers having different degrees ortypes of crimping, or both. For example, one embodiment may include amixture of fibers having about 8 to about 12 crimps per inch (cpi) orabout 9 to about 10 cpi, and other fibers having about 4 to about 8 cpior about 5 to about 7 cpi. Different types of crimps include, but arenot limited to a 2D crimp or “flat crimp” and a 3D or spiral-crimp.According to a certain embodiment, the fibers may include bi-componentfibers, which are individual fibers each comprising different materials,usually a first and a second polymeric material. It is believed that theuse of side-by-side bi-component fibers is beneficial for imparting aspiral-crimp to the fibers.

The upper acquisition layer 52 may be stabilized by a latex binder, forexample a styrene-butadiene latex binder (SB latex), in a certainembodiment. Processes for obtaining such lattices are known, forexample, from EP 149 880 (Kwok) and US 2003/0105190 (Diehl et al.). Incertain embodiments, the binder may be present in the upper acquisitionlayer 52 in excess of about 12%, about 14% or about 16% by weight. Forcertain embodiments, SB latex is available under the trade name GENFLO™3160 (OMNOVA Solutions Inc.; Akron, Ohio).

The absorbent core 14 in FIGS. 1-8 generally is disposed between thetopsheet 18 and the backsheet 20 and comprises two layers, a firstabsorbent layer 60 and a second absorbent layer 62. As best shown inFIG. 3, the first absorbent layer 60 of the absorbent core 14 comprisesa substrate 64, an absorbent particular polymer material 66 on thesubstrate 64, and a thermoplastic composition 68 on the absorbentparticulate polymer material 66 and at least portions of the firstsubstrate 64 as an adhesive for covering and immobilizing the absorbentparticulate polymer material 66 on the first substrate 64. According toanother embodiment illustrated in FIG. 4, the first absorbent layer 60of the absorbent core 14 may also include a cover layer 70 on thethermoplastic composition 68.

Likewise, as best illustrated in FIG. 2, the second absorbent layer 62of the absorbent core 14 may also include a substrate 72, an absorbentparticulate polymer material 74 on the second substrate 72, and athermoplastic composition 66 on the absorbent particulate polymermaterial 74 and at least a portion of the second substrate 72 forimmobilizing the absorbent particulate polymer material 74 on the secondsubstrate 72. Although not illustrated, the second absorbent layer 62may also include a cover layer such as the cover layer 70 illustrated inFIG. 4.

The substrate 64 of the first absorbent layer 60 may be referred to as adusting layer and has a first surface 78 which faces the backsheet 20 ofthe diaper 10 and a second surface 80 which faces the absorbentparticulate polymer material 66. Likewise, the substrate 72 of thesecond absorbent layer 62 may be referred to as a core cover and has afirst surface 82 facing the topsheet 18 of the diaper 10 and a secondsurface 84 facing the absorbent particulate polymer material 74. Thefirst and second substrates 64 and 72 may be adhered to one another withadhesive about the periphery to form an envelope about the absorbentparticulate polymer materials 66 and 74 to hold the absorbentparticulate polymer material 66 and 74 within the absorbent core 14.

According to a certain embodiment, the substrates 64 and 72 of the firstand second absorbent layers 60 and 62 may be a non-woven material, suchas those nonwoven materials described above. In certain embodiments, thenon-wovens are porous and in one embodiment has a pore size of about 32microns.

As illustrated in FIGS. 1-8, the absorbent particulate polymer material66 and 74 is deposited on the respective substrates 64 and 72 of thefirst and second absorbent layers 60 and 62 in clusters 90 of particlesto form a grid pattern 92 comprising land areas 94 and junction areas 96between the land areas 94. As defined herein, land areas 94 are areaswhere the thermoplastic adhesive material does not contact the nonwovensubstrate or the auxiliary adhesive directly; junction areas 96 areareas where the thermoplastic adhesive material does contact thenonwoven substrate or the auxiliary adhesive directly. The junctionareas 96 in the grid pattern 92 contain little or no absorbentparticulate polymer material 66 and 74. The land areas 94 and junctionareas 96 can have a variety of shapes including, but not limited to,circular, oval, square, rectangular, triangular, and the like.

The grid pattern shown in FIG. 8 is a square grid with regular spacingand size of the land areas. Other grid patterns including hexagonal,rhombic, orthorhombic, parallelogram, triangular, rectangular, andcombinations thereof may also be used. The spacing between the gridlines may be regular or irregular.

The size of the land areas 94 in the grid patterns 92 may vary.According to certain embodiments, the width 119 of the land areas 94 inthe grid patterns 92 ranges from about 8 mm to about 12 mm. In a certainembodiment, the width of the land areas 94 is about 10 mm. The junctionareas 96, on the other hand, in certain embodiments, have a width orlarger span of less than about 5 mm, less than about 3 mm, less thanabout 2 mm, less than about 1.5 mm, less than about 1 mm, or less thanabout 0.5 mm.

As shown in FIG. 8, the absorbent core 14 has a longitudinal axis 100extending from a rear end 102 to a front end 104 and a transverse axis106 perpendicular to the longitudinal axis 100 extending from a firstedge 108 to a second edge 110. The grid pattern 92 of absorbentparticulate polymer material clusters 90 is arranged on the substrates64 and 72 of the respective absorbent layers 60 and 62 such that thegrid pattern 92 formed by the arrangement of land areas 94 and junctionareas 96 forms a pattern angle 112. The pattern angle 112 may be 0,greater than 0, or 15 to 30 degrees, or from about 5 to about 85degrees, or from about 10 to about 60 degrees, or from about 15 to about30 degrees.

As best seen in FIGS. 7 a, 7 b, and 8, the first and second layers 60and 62 may be combined to form the absorbent core 14. The absorbent core14 has an absorbent particulate polymer material area 114 bounded by apattern length 116 and a pattern width 118. The extent and shape of theabsorbent particulate polymer material area 114 may vary depending onthe desired application of the absorbent core 14 and the particularabsorbent article in which it may be incorporated. In a certainembodiment, however, the absorbent particulate polymer material area 114extends substantially entirely across the absorbent core 14, such as isillustrated in FIG. 8.

The first and second absorbent layers 60 and 62 may be combined togetherto form the absorbent core 14 such that the grid patterns 92 of therespective first and second absorbent layers 62 and 64 are offset fromone another along the length and/or width of the absorbent core 14. Therespective grid patterns 92 may be offset such that the absorbentparticulate polymer material 66 and 74 is substantially continuouslydistributed across the absorbent particulate polymer area 114. In acertain embodiment, absorbent particulate polymer material 66 and 74 issubstantially continuously distributed across the absorbent particulatepolymer material area 114 despite the individual grid patterns 92comprising absorbent particulate polymer material 66 and 74discontinuously distributed across the first and second substrates 64and 72 in clusters 90. In a certain embodiment, the grid patterns may beoffset such that the land areas 94 of the first absorbent layer 60 facethe junction areas 96 of the second absorbent layer 62 and the landareas of the second absorbent layer 62 face the junction areas 96 of thefirst absorbent layer 60. When the land areas 94 and junction areas 96are appropriately sized and arranged, the resulting combination ofabsorbent particulate polymer material 66 and 74 is a substantiallycontinuous layer of absorbent particular polymer material across theabsorbent particulate polymer material area 114 of the absorbent core 14(i.e. first and second substrates 64 and 72 do not form a plurality ofpockets, each containing a cluster 90 of absorbent particulate polymermaterial 66 therebetween). In a certain embodiment, respective gridpatterns 92 of the first and second absorbent layer 60 and 62 may besubstantially the same.

In a certain embodiment as illustrated in FIG. 8, the amount ofabsorbent particulate polymer material 66 and 74 may vary along thelength 116 of the grid pattern 92. In a certain embodiment, the gridpattern may be divided into absorbent zones 120, 122, 124, and 126, inwhich the amount of absorbent particulate polymer material 66 and 74varies from zone to zone. As used herein, “absorbent zone” refers to aregion of the absorbent particulate polymer material area havingboundaries that are perpendicular to the longitudinal axis shown in FIG.8. The amount of absorbent particulate polymer material 66 and 74 may,in a certain embodiment, gradually transition from one of the pluralityof absorbent zones 120, 122, 124, and 126 to another. This gradualtransition in amount of absorbent particulate polymer material 66 and 74may reduce the possibility of cracks forming in the absorbent core 14.

The amount of absorbent particulate polymer material 66 and 74 presentin the absorbent core 14 may vary, but in certain embodiments, ispresent in the absorbent core in an amount greater than about 80% byweight of the absorbent core, or greater than about 85% by weight of theabsorbent core, or greater than about 90% by weight of the absorbentcore, or greater than about 95% by weight of the core. In a particularembodiment, the absorbent core 14 consists essentially of the first andsecond substrates 64 and 72, the absorbent particulate polymer material66 and 74, and the thermoplastic adhesive composition 68 and 76. In anembodiment, the absorbent core 14 may be substantially cellulose free.

According to certain embodiments, the weight of absorbent particulatepolymer material 66 and 74 in at least one freely selected first squaremeasuring 1 cm×1 cm may be at least about 10%, or 20%, or 30%, 40% or50% higher than the weight of absorbent particulate polymer material 66and 74 in at least one freely selected second square measuring 1 cm×1cm. In a certain embodiment, the first and the second square arecentered about the longitudinal axis.

The absorbent particulate polymer material area, according to anexemplary embodiment, may have a relatively narrow width in the crotcharea of the absorbent article for increased wearing comfort. Hence, theabsorbent particulate polymer material area, according to an embodiment,may have a width as measured along a transverse line which is positionedat equal distance to the front edge and the rear edge of the absorbentarticle, which is less than about 100 mm, 90 mm, 80 mm, 70 mm, 60 mm oreven less than about 50 mm.

It has been found that, for most absorbent articles such as diapers, theliquid discharge occurs predominately in the front half of the diaper.The front half of the absorbent core 14 should therefore comprise mostof the absorbent capacity of the core. Thus, according to certainembodiments, the front half of said absorbent core 14 may comprise morethan about 60% of the superabsorbent material, or more than about 65%,70%, 75%, 80%, 85%, or 90% of the superabsorbent material.

In certain embodiments, the absorbent core 14 may further comprise anyabsorbent material that is generally compressible, conformable,non-irritating to the wearer's skin, and capable of absorbing andretaining liquids such as urine and other certain body exudates. In suchembodiments, the absorbent core 14 may comprise a wide variety ofliquid-absorbent materials commonly used in disposable diapers and otherabsorbent articles such as comminuted wood pulp, which is generallyreferred to as airfelt, creped cellulose wadding, melt blown polymers,including co-form, chemically stiffened, modified or cross-linkedcellulosic fibers, tissue, including tissue wraps and tissue laminates,absorbent foams, absorbent sponges, or any other known absorbentmaterial or combinations of materials. The absorbent core 14 may furthercomprise minor amounts (typically less than about 10%) of materials,such as adhesives, waxes, oils and the like.

Exemplary absorbent structures for use as the absorbent assemblies aredescribed in U.S. Pat. No. 4,610,678 (Weisman et al.); U.S. Pat. No.4,834,735 (Alemany et al.); U.S. Pat. No. 4,888,231 (Angstadt); U.S.Pat. No. 5,260,345 (DesMarais et al.); U.S. Pat. No. 5,387,207 (Dyer etal.); U.S. Pat. No. 5,397,316 (LaVon et al.); and U.S. Pat. No.5,625,222 (DesMarais et al.).

The thermoplastic adhesive material 68 and 76 may serve to cover and atleast partially immobilize the absorbent particulate polymer material 66and 74. In one embodiment of the present invention, the thermoplasticadhesive material 68 and 76 can be disposed essentially uniformly withinthe absorbent particulate polymer material 66 and 74, between thepolymers. However, in a certain embodiment, the thermoplastic adhesivematerial 68 and 76 may be provided as a fibrous layer which is at leastpartially in contact with the absorbent particulate polymer material 66and 74 and partially in contact with the substrate layers 64 and 72 ofthe first and second absorbent layers 60 and 62. FIGS. 3, 4, and 7 showsuch a structure, and in that structure, the absorbent particulatepolymer material 66 and 74 is provided as a discontinuous layer, and alayer of fibrous thermoplastic adhesive material 68 and 76 is laid downonto the layer of absorbent particulate polymer material 66 and 74, suchthat the thermoplastic adhesive material 68 and 76 is in direct contactwith the absorbent particulate polymer material 66 and 74, but also indirect contact with the second surfaces 80 and 84 of the substrates 64and 72, where the substrates are not covered by the absorbentparticulate polymer material 66 and 74. This imparts an essentiallythree-dimensional structure to the fibrous layer of thermoplasticadhesive material 68 and 76, which in itself is essentially atwo-dimensional structure of relatively small thickness, as compared tothe dimension in length and width directions. In other words, thethermoplastic adhesive material 68 and 76 undulates between theabsorbent particulate polymer material 68 and 76 and the second surfacesof the substrates 64 and 72.

Thereby, the thermoplastic adhesive material 68 and 76 may providecavities to cover the absorbent particulate polymer material 66 and 74,and thereby immobilizes this material. In a further aspect, thethermoplastic adhesive material 68 and 76 bonds to the substrates 64 and72 and thus affixes the absorbent particulate polymer material 66 and 74to the substrates 64 and 72. Thus, in accordance with certainembodiments, the thermoplastic adhesive material 68 and 76 immobilizesthe absorbent particulate polymer material 66 and 74 when wet, such thatthe absorbent core 14 achieves an absorbent particulate polymer materialloss of no more than about 70%, 60%, 50%, 40%, 30%, 20%, 10% accordingto the Wet Immobilization Test described herein. Some thermoplasticadhesive materials will also penetrate into both the absorbentparticulate polymer material 66 and 74 and the substrates 64 and 72,thus providing for further immobilization and affixation. Of course,while the thermoplastic adhesive materials disclosed herein provide amuch improved wet immobilization (i.e., immobilization of absorbentmaterial when the article is wet or at least partially loaded), thesethermoplastic adhesive materials may also provide a very goodimmobilization of absorbent material when the absorbent core 14 is dry.The thermoplastic adhesive material 68 and 76 may also be referred to asa hot melt adhesive.

Without wishing to be bound by theory, it has been found that thosethermoplastic adhesive materials which are most useful for immobilizingthe absorbent particulate polymer material 66 and 74 combine goodcohesion and good adhesion behavior. Good adhesion may promote goodcontact between the thermoplastic adhesive material 68 and 76 and theabsorbent particulate polymer material 66 and 74 and the substrates 64and 72. Good cohesion reduces the likelihood that the adhesive breaks,in particular in response to external forces, and namely in response tostrain. When the absorbent core 14 absorbs liquid, the absorbentparticulate polymer material 66 and 74 swells and subjects thethermoplastic adhesive material 68 and 76 to external forces. In certainembodiments, the thermoplastic adhesive material 68 and 76 may allow forsuch swelling, without breaking and without imparting too manycompressive forces, which would restrain the absorbent particulatepolymer material 66 and 74 from swelling.

In accordance with certain embodiments, the thermoplastic adhesivematerial 68 and 76 may comprise, in its entirety, a single thermoplasticpolymer or a blend of thermoplastic polymers, having a softening point,as determined by the ASTM Method D-36-95 “Ring and Ball”, in the rangebetween 50° C. and 300° C., or alternatively the thermoplastic adhesivematerial may be a hot melt adhesive comprising at least onethermoplastic polymer in combination with other thermoplastic diluentssuch as tackifying resins, plasticizers and additives such asantioxidants. In certain embodiments, the thermoplastic polymer hastypically a molecular weight (Mw) of more than 10,000 and a glasstransition temperature (Tg) usually below room temperature or −6°C.>Tg<16° C. In certain embodiments, typical concentrations of thepolymer in a hot melt are in the range of about 20 to about 40% byweight. In certain embodiments, thermoplastic polymers may be waterinsensitive. Exemplary polymers are (styrenic) block copolymersincluding A-B-A triblock structures, A-B diblock structures and(A-B)_(n) radial block copolymer structures wherein the A blocks arenon-elastomeric polymer blocks, typically comprising polystyrene, andthe B blocks are unsaturated conjugated diene or (partly) hydrogenatedversions of such. The B block is typically isoprene, butadiene,ethylene/butylene (hydrogenated butadiene), ethylene/propylene(hydrogenated isoprene), and mixtures thereof.

Other suitable thermoplastic polymers that may be employed aremetallocene polyolefins, which are ethylene polymers prepared usingsingle-site or metallocene catalysts. Therein, at least one comonomercan be polymerized with ethylene to make a copolymer, terpolymer orhigher order polymer. Also applicable are amorphous polyolefins oramorphous polyalphaolefins (APAO) which are homopolymers, copolymers orterpolymers of C2 to C8 alpha olefins.

In exemplary embodiments, the tackifying resin has typically a Mw below5,000 and a Tg usually above room temperature, typical concentrations ofthe resin in a hot melt are in the range of about 30 to about 60%, andthe plasticizer has a low Mw of typically less than 1,000 and a Tg belowroom temperature, with a typical concentration of about 0 to about 15%.

In certain embodiments, the thermoplastic adhesive material 68 and 76 ispresent in the form of fibers. In some embodiments, the fibers will havean average thickness of about 1 to about 50 micrometers or about 1 toabout 35 micrometers and an average length of about 5 mm to about 50 mmor about 5 mm to about 30 mm. To improve the adhesion of thethermoplastic adhesive material 68 and 76 to the substrates 64 and 72 orto any other layer, in particular any other non-woven layer, such layersmay be pre-treated with an auxiliary adhesive.

In certain embodiments, the thermoplastic adhesive material 68 and 76will meet at least one, or several, or all of the following parameters:

An exemplary thermoplastic adhesive material 68 and 76 may have astorage modulus G′ measured at 20° C. of at least 30,000 Pa and lessthan 300,000 Pa, or less than 200,000 Pa, or between 140,000 Pa and200,000 Pa, or less than 100,000 Pa. In a further aspect, the storagemodulus G′ measured at 35° C. may be greater than 80,000 Pa. In afurther aspect, the storage modulus G′ measured at 60° C. may be lessthan 300,000 Pa and more than 18,000 Pa, or more than 24,000 Pa, or morethan 30,000 Pa, or more than 90,000 Pa. In a further aspect, the storagemodulus G′ measured at 90° C. may be less than 200,000 Pa and more than10,000 Pa, or more than 20,000 Pa, or more then 30,000 Pa. The storagemodulus measured at 60° C. and 90° C. may be a measure for the formstability of the thermoplastic adhesive material at elevated ambienttemperatures. This value is particularly important if the absorbentproduct is used in a hot climate where the thermoplastic adhesivematerial would lose its integrity if the storage modulus G′ at 60° C.and 90° C. is not sufficiently high.

G′ is measured using a rheometer as schematically shown in FIG. 9 forthe purpose of general illustration only. The rheometer 127 is capableof applying a shear stress to the adhesive and measuring the resultingstrain (shear deformation) response at constant temperature. Theadhesive is placed between a Peltier-element acting as lower, fixedplate 128 and an upper plate 129 with a radius R of e.g., 10 mm, whichis connected to the drive shaft of a motor to generate the shear stress.The gap between both plates has a height H of e.g., 1500 micron. ThePeltier-element enables temperature control of the material (+0.5° C.).The strain rate and frequency should be chosen such that allmeasurements are made in the linear viscoelastic region.

The absorbent core 14 may also comprise an auxiliary adhesive which isnot illustrated in the figures. The auxiliary adhesive may be depositedon the first and second substrates 64 and 72 of the respective first andsecond absorbent layers 60 and 62 before application of the absorbentparticulate polymer material 66 and 74 for enhancing adhesion of theabsorbent particulate polymer materials 66 and 74 and the thermoplasticadhesive material 68 and 76 to the respective substrates 64 and 72. Theauxiliary glue may also aid in immobilizing the absorbent particulatepolymer material 66 and 74 and may comprise the same thermoplasticadhesive material as described hereinabove or may also comprise otheradhesives including but not limited to sprayable hot melt adhesives,such as H.B. Fuller Co. (St. Paul, Minn.) Product No. HL-1620-B. Theauxiliary glue may be applied to the substrates 64 and 72 by anysuitable means, but according to certain embodiments, may be applied inabout 0.5 to about 1 mm wide slots spaced about 0.5 to about 2 mm apart.

The cover layer 70 shown in FIG. 4 may comprise the same material as thesubstrates 64 and 72, or may comprise a different material. In certainembodiments, suitable materials for the cover layer 70 are the non-wovenmaterials, typically the materials described above as useful for thesubstrates 64 and 72.

A printing system 130 for making an absorbent core 14 in accordance withan embodiment of this invention is illustrated in FIG. 10 and maygenerally comprise a first printing unit 132 for forming the firstabsorbent layer 60 of the absorbent core 14 and a second printing unit134 for forming the second absorbent layer 62 of the absorbent core 14.

The first printing unit 132 may comprise a first auxiliary adhesiveapplicator 136 for applying an auxiliary adhesive to the substrate 64,which may be a nonwoven web, a first rotatable support roll 140 forreceiving the substrate 64, a hopper 142 for holding absorbentparticulate polymer material 66, a printing roll 144 for transferringthe absorbent particulate polymer material 66 to the substrate 64, and athermoplastic adhesive material applicator 146 for applying thethermoplastic adhesive material 68 to the substrate 64 and the absorbentparticulate polymer 66 material thereon.

The second printing unit 134 may comprise a second auxiliary adhesiveapplicator 148 for applying an auxiliary adhesive to the secondsubstrate 72, a second rotatable support roll 152 for receiving thesecond substrate 72, a second hopper 154 for holding the absorbentparticulate polymer material 74, a second printing roll 156 fortransferring the absorbent particulate polymer material 74 from thehopper 154 to the second substrate 72, and a second thermoplasticadhesive material applicator 158 for applying the thermoplastic adhesivematerial 76 to the second substrate 72 and the absorbent particulatepolymer material 74 thereon.

The printing system 130 also includes a guide roller 160 for guiding theformed absorbent core from a nip 162 between the first and secondrotatable support rolls 140 and 152.

The first and second auxiliary applicators 136 and 148 and the first andsecond thermoplastic adhesive material applicators 146 and 158 may be anozzle system which can provide a relatively thin but wide curtain ofthermoplastic adhesive material.

Turning to FIG. 11, portions of the first hopper 142, first support roll140, and first printing roll 144 are illustrated. As also shown in FIG.14, the first rotatable support roll 140, which has the same structureas the second rotatable support roll 152, comprises a rotatable drum 164and a peripheral vented support grid 166 for receiving the firstsubstrate 64.

As also illustrated in FIG. 12, the first printing roll 144, which hasthe same structure as the second printing roll 156, comprises arotatable drum 168 and a plurality of absorbent particulate polymermaterial reservoirs 170 in a peripheral surface 172 of the drum 168. Thereservoirs 170 best illustrated in FIG. 13, may have a variety ofshapes, including cylindrical, conical, or any other shape. Thereservoirs 170 may lead to an air passage 174 in the drum 168 andcomprise a vented cover 176 for holding adhesive particulate polymermaterial 66 in the reservoir and preventing the adhesive particulatepolymer material 66 from falling or being pulled into the air passage174.

In operation, the printing system 130 receives the first and secondsubstrate 64 and 72 into the first and second printing units 132 and134, respectively, the first substrate 64 is drawn by the rotating firstsupport roll 140 past the first auxiliary adhesive applicator 136 whichapplies the first auxiliary adhesive to the first substrate 64 in apattern such as described hereinabove. A vacuum (not shown) within thefirst support roll 140 draws the first substrate 64 against the verticalsupport grid 166 and holds the first substrate 64 against the firstsupport roll 140. This presents an uneven surface on the first substrate64. Due to gravity, or by using the vacuum means, the substrate 64 willfollow the contours of the uneven surface and thereby the substrate 64will assume a mountain and valley shape. The absorbent particulatepolymer material 66 may accumulate in the valleys presented by thesubstrate 64. The first support roll 140 then carries the firstsubstrate 64 past the rotating first printing roll 144 which transfersthe absorbent particulate polymer material 66 from the first hopper 142to the first substrate 64 in the grid pattern 92 which is bestillustrated in FIGS. 5 and 6. A vacuum (not shown) in the first printingroll 144 may hold the absorbent particulate polymer material 66 in thereservoirs 170 until time to deliver the absorbent particulate polymermaterial 66 to the first substrate 64. The vacuum may then be releasedor air flow through the air passages 174 may be reversed to eject theabsorbent particulate polymer material 66 from the reservoirs and ontothe first substrate 64. The absorbent particulate polymer material 66may accumulate in the valleys presented by the substrate 64. The supportroll 140 then carries the printed first substrate 64 past thethermoplastic adhesive material applicator 136 which applies thethermoplastic adhesive material 68 to cover the absorbent particulatepolymer material 66 on the first substrate 64.

Hence, the uneven surface of the vented support grid 166 of the supportrolls 140 and 152 determines the distribution of absorbent particulatepolymeric material 66 and 74 throughout the absorbent core 14 andlikewise determines the pattern of junction areas 96.

Meanwhile, the second rotatable support roll draws the second substrate72 past the second auxiliary adhesive applicator 148 which applies anauxiliary adhesive to the second substrate 72 in a pattern such as isdescribed hereinabove. The second rotatable support roll 152 thencarries the second substrate 72 past the second printing roll 156 whichtransfers the absorbent particulate polymer material 74 from the secondhopper 154 to the second substrate 72 and deposits the absorbentparticulate polymer material 74 in the grid pattern 92 on the secondsubstrate 72 in the same manner as described with regard to the firstprinting unit 132 above. The second thermoplastic adhesive materialapplicator 158 then applies the thermoplastic adhesive material 76 tocover the absorbent particulate polymer material 74 on the secondsubstrate 72. The printed first and second substrates 64 and 72 thenpass through the nip 162 between the first and second support rolls 140and 152 for compressing the first absorbent layer 60 and secondabsorbent layer 62 together to form the absorbent core 14.

In an optional further process step a cover layer 70 may be placed uponthe substrates 64 and 72, the absorbent particulate polymer material 66and 74, and the thermoplastic adhesive material 68 and 76. In anotherembodiment, the cover layer 70 and the respective substrate 64 and 72may be provided from a unitary sheet of material. The placing of thecover layer 70 onto the respective substrate 64 and 72 may then involvethe folding of the unitary piece of material.

The test method and apparatuses described below may be useful in testingembodiments of this invention:

Wet Immobilization Test

Equipment

-   -   Graduated Cylinder    -   Stop watch (±0.1 sec)    -   Scissors    -   Light Box    -   Pen    -   Test solution: 0.90% saline solution at 37° C.    -   Metal ruler traceable to NIST, DIN, JIS or other comparable        National Standard    -   PVC/metal dishes with a flat surface inside and a minimum length        of the core bag length (n) to be measured and a maximum length        n+30 mm, width of 105±5 mm, height of 30 −80 mm or equivalent    -   Electronic Force Gauge (Range 0 to 50 Kg)    -   Wet Immobilization Impact Tester Equipment (WAIIT), Design        package number: BM-00112.59500-R01 available from T.M.G.        Technisches Buero Manfred Gruna        Facilities:

Standard laboratory conditions, temperature: 23° C.±2° C., relativehumidity: <55%

Sample Preparation

-   -   1. Open the product, topsheet side up.    -   2. Unfold the diaper and cut the cuff elastics approximately        every 2.5 cm to avoid chassis tension.    -   3. For pull-up products open the side seams and remove the        waistbands.    -   4. Lay the core bag flat and rectangular topsheet side up onto        the light box surface without any folds.    -   5. Switch on the light box to clearly identify the absorbent        core outer edges.    -   6. With a ruler, draw a line at the front and back absorbent        core outer edges.    -   7. Measure the distance (A), between the two markers and divide        the value by 2, this will be calculated distance (B).    -   8. Measure the calculated distance (B) from front marker towards        the middle of the core bag and mark it. At this marker draw a        line in the cross direction.        Test Procedure        WAIIT Calibration:    -   1. Make sure that the sliding board is in the lower position.        Open the front door of the WAIIT tester and connect the force        gauge hook to the upper sample clamp of the WAIIT. Make sure        that the clamp is closed before connecting the spring-balance.    -   2. Use both hands on the spring-balance to lift continuously and        as slowly as possible up the sliding board towards the upper        position. Record the average value (m₁) during the execution to        the nearest 0.02 kg.    -   3. Guide down the sliding board as slowly as possible to the        lower position and record the average value (m₂) read off during        execution to the nearest 0.02 kg.    -   4. Calculate and report the delta of m₁-m₂ to the nearest 0.01        kg. If the delta is 0.6 kg±0.3 kg continue measurement.        Otherwise, an adjustment of the sliding board is necessary. Make        sure that the sliding board is in lower position and check the        sliding path for any contamination or damage. Check if the        position of the sliding board to the sliding path is correctly        adjusted by shaking the board. For easy gliding some clearance        is needed. If not present, readjust the system.        WAIIT Test Settings:    -   Drop height is 50 cm.    -   Diaper load (I_(D)) is 73% of the core capacity (cc);        I_(D)=0.73×cc.    -   Core capacity (cc) is calculated as: cc=m_(SAP)×SAP_(GV), where        m_(SAP) is the mass of superabsorbent polymer (SAP) present in        the diaper and SAP_(GV) is the free swelling capacity of the        superabsorbent polymer. Free swelling capacity of the        superabsorbent polymer is determined with the method described        in WO 2006/062258. The mass of the superabsorbent polymer        present in the diaper is the average mass present in ten        products.        Test execution:    -   1. Reset the balance to zero (tare), put the dry core bag on the        balance, weigh and report it to the nearest 0.1 g.    -   2. Measure the appropriate volume Saline (0.9% NaCl in deionized        water) with the graduated cylinder.    -   3. Lay the core bag, topsheet side up, flat into the PVC dish.        Pour the saline evenly over the core bag.    -   4. Take the PVC dish and hold it slanting in different        directions, to allow any free liquid to be absorbed. Products        with poly-backsheet need to be turned after a minimum waiting        time of 2 minutes so that liquid under the backsheet can be        absorbed. Wait for 10 minutes (+/−1 minute) to allow all saline        to be absorbed. Some drops may retain in the PVC dish. Use only        the defined PVC/metal dish to guarantee homogenous liquid        distribution and less retained liquid.    -   5. Reset the balance to zero (tare), put the wet core bag on the        balance. Weigh and report it to the nearest 0.1 g. Fold the core        bag just once to make it fit on the balance. Check to see if the        wet core bag weight is out of limit (defined as “dry core bag        weight+diaper load±4 ml”). For example, 12 g dry core bag        weight+150 ml load=162 g wet core bag weight. If the actual wet        weight on the scale is between 158 g and 166 g, the pad can be        used for shaking. Otherwise scrap the pad and use the next one.    -   6. Take the loaded core bag and cut the pad along the marked        line in the cross direction.    -   7. Put the back of the wet core bag onto the balance (ml). Weigh        and report it to the nearest 0.1 g.    -   8. Take the wet core and clamp the end seal side in the top        clamp of the sample holder of the WAIIT (open end of the core        oriented down). Next, clamp both sides of the core with the side        clamps of the sample holder making sure that the product is        fixed to the sample holder along the whole product length. Make        sure not to clamp the absorbent core, only the nonwoven; for        some products this means securing the product with only the        barrier leg cuff.    -   9. Lift up the sliding board to the upper position by using both        hands until the board is engaged.    -   10. Close the safety front door and release the slide blade.    -   11. Reset the balance to zero (tare), take the tested core bag        out of the WAIIT and put it on the balance (m₂). Report the        weight to the nearest 0.1 g.    -   12. Repeat steps 7 to 11 with front of the wet core bag.        Reporting:    -   1. Record the dry core bag weight to the nearest 0.1 g.    -   2. Record the wet weight before (m_(1 front/back)) and after        (m_(2 front/back)) testing, both to the nearest 0.1 g.    -   3. Calculate and report the average weight loss (Δm) to the        nearest 0.1 g:        Δm=(m_(1 front)+m_(1 back))−(m_(2 front)+m_(2back))    -   4. Calculate and report the weight loss in percent to the        nearest 1%, (Δm_(rel)):        (Δm_(rel))=(((m_(1front)+m_(1back))−(m_(2front)+m_(2back)))×100)/(m_(1front)+m_(1back))    -   5. Calculate and report Wet Immobilization (WI) as:        WI=100%−Δm_(rel)

All patents and patent applications (including any patents which issuethereon) assigned to the Procter & Gamble Company referred to herein arehereby incorporated by reference to the extent that it is consistentherewith.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention. To the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A disposable absorbent article comprising: achassis including a topsheet and a backsheet; and a substantiallycellulose free absorbent core located between the topsheet and thebacksheet and including first and second absorbent layers, the firstabsorbent layer including a first substrate and the second absorbentlayer including a second substrate, the first and second absorbentlayers further including absorbent particulate polymer materialdeposited on said first and second substrates and thermoplastic adhesivematerial covering the absorbent particulate polymer material on therespective first and second substrates, said first and second absorbentlayers combined together such that at least a portion of saidthermoplastic adhesive material of said first absorbent layer contactsat least a portion of the thermoplastic adhesive material of said secondabsorbent layer, the absorbent particulate polymer material is disposedbetween the first and second substrates in an absorbent particulatepolymer material area, and the absorbent particulate polymer material issubstantially continuously distributed across the absorbent particulatepolymer material area; wherein the absorbent particulate polymermaterial is deposited on the first and second substrates in respectivepatterns of land areas and junction areas between the land areas suchthat the absorbent particulate polymer material is discontinuouslydistributed on the first and second substrates; and the first and secondabsorbent layers are combined together such that the respective patternsof absorbent particulate polymer material are offset from one another;wherein the absorbent core has a front end and a rear end and alongitudinal axis extending from the rear end to the front end and theland areas of the respective patterns are arranged in a grid which ispositioned at an angle from about 5 to about 85 degrees from thelongitudinal axis of the absorbent core; wherein the width of the landareas is from about 8mm to about 12mm and the width of the junctionareas is less than about 5mm; wherein the absorbent core has fourabsorbent zones disposed along said longitudinal axis of said absorbentcore, each of the four absorbent zones having absorbent particulatepolymer material present in differing amounts between the four absorbentzones and each of the four absorbent zones is substantially cellulosefree; wherein there is a gradual transition in amount of absorbentparticulate polymer material from one of the four absorbent zones toanother.
 2. The disposable absorbent article of claim 1, wherein theabsorbent particulate polymer material area extends substantiallyentirely across the absorbent core.
 3. The disposable absorbent articleof claim 1, wherein the absorbent particulate polymer material areaextends substantially entirely from front to back of the absorbent core.4. The disposable absorbent article of claim 1, wherein the respectivepatterns are substantially the same.
 5. The disposable absorbent articleof claim 1, wherein the respective patterns are different.
 6. Thedisposable absorbent article of claim 1, wherein the absorbent coreconsists essentially of the first and second substrates, the absorbentparticulate polymer material, and the thermoplastic adhesive material.7. The disposable absorbent article of claim 1, wherein the backsheethas a water vapor transmission rate of greater than about 3000 g/24 h/m²according to the test described herein.
 8. The disposable absorbentarticle of claim 1 having an absorbent particulate polymer material lossof no more than about 70% according to the Wet Immobilization Testherein.
 9. The disposable absorbent article of claim 1, wherein theabsorbent particulate polymer material is present in the absorbent corein an amount greater than about 80% by weight of the absorbent core. 10.The disposable absorbent article of claim 1, wherein the absorbent corehas a length extending from a rear end to a front end, and a widthextending from a first edge to a second edge and perpendicularly to thelength, and the respective patterns are offset from one another in botha direction parallel to the length and d direction parallel to thewidth.
 11. The disposable absorbent article of claim 1, wherein theabsorbent article is a diaper comprising a re-closable fastening systemjoined to the chassis for securing the diaper to a wearer.
 12. Thedisposable absorbent article of claim 1, wherein the absorbent articleis a pant-type diaper comprising at least two side panels joined to thechassis and to each other to form a pant.
 13. An absorbent corecomprising first and second absorbent layers, the first absorbent layerincluding a first substrate and the second absorbent layer including asecond substrate, the first and second absorbent layers furtherincluding absorbent particulate polymer material deposited on said firstand second substrates and thermoplastic adhesive material covering theabsorbent particulate polymer material on the respective first andsecond substrates, said first and second absorbent layers combinedtogether such that at least a portion of said thermoplastic adhesivematerial of said first absorbent layer contacts at least a portion ofthe thermoplastic adhesive material of said second absorbent layer, theabsorbent particulate polymer material is disposed between the first andsecond substrates in an absorbent particulate polymer material area, andthe absorbent particulate polymer material is substantially continuouslydistributed across the absorbent particulate polymer material area,wherein the absorbent core is substantially cellulose free; wherein theabsorbent particulate polymer material is deposited on the first andsecond substrates in respective patterns of land areas and junctionareas between the land areas such that the absorbent particulate polymermaterial is discontinuously distributed on the first and secondsubstrates; and the first and second absorbent layers are combinedtogether such that the respective patterns of absorbent particulatepolymer material are offset from one another; wherein the absorbent corehas a front end and a rear end and a longitudinal axis extending fromthe rear end to the front end and the land areas of the respectivepatterns are arranged in a grid which is positioned at an angle fromabout 5 to about 85 degrees from the longitudinal axis of the absorbentcore; wherein the width of the land areas is from about 8mm to about12mm and the width of the junction areas is less than about 5mm; whereinthe absorbent core has four absorbent zones disposed along saidlongitudinal axis of said absorbent core, each of the four absorbentzones having absorbent particulate polymer material present in differingamounts between the four absorbent zones and each of the four absorbentzones is substantially cellulose free; wherein there is a gradualtransition in amount of absorbent particulate polymer material from oneof the four absorbent zones to another.